1. Field of the Invention
This application relates to a belt drive device and an image forming apparatus including the belt drive device.
2. Description of the Related Art
An image forming apparatus that incorporates a belt drive device, which drives a transfer belt that transports a sheet as a recording medium and transfers a toner image to the sheet, is well known. In the image forming apparatus, an image pattern used for correcting image density or a color shift is formed on the transfer belt and is detected by a detection sensor. Japanese Patent Laid-Open No. 2004-258281 discloses one such belt drive device.
In the aforementioned belt drive device, however, the distance between the detection sensor and the transfer belt is liable to vary due to plastic deformation of the transfer belt. When the plastic deformation is induced on the transfer belt, the detection sensor is unable to detect the image pattern properly, resulting in insufficient correction of the image density or the color shift. This will cause adverse effects on image quality.